Dual Mono wiring for a Vout DAC

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themystical

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Joined 2006
#1
Can somebody please help me with the correct configuration of a wiring the analogue outputs of a dual mono Vout DAC?
I know for a current output DAC its a parallel connection,the Right + is connected to Left + and Right - is connected to L-.
Instinctively, the connection for a Vout DAC is a series connection? ie. R- connected to L+?
However the AKM 4497 Datasheet seems to show a parallel connection, same as a current output DAC? (see attached excerpt)
 

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  • AK4497 Dual Mono Wiring.JPG
    AK4497 Dual Mono Wiring.JPG
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#4
Judging by the ultra-low values of the Rs in that schematic, its been designed to give the highest SNR measurement possible. However the consequent loading on the DAC chip's opamps suggests SQ (dynamics in particular) is going to suffer rather badly.

Do you want to listen to this DAC or get the best possible measurements?
 
#5
abraxalito said:
Judging by the ultra-low values of the Rs in that schematic, its been designed to give the highest SNR measurement possible. However the consequent loading on the DAC chip's opamps suggests SQ (dynamics in particular) is going to suffer rather badly.

Do you want to listen to this DAC or get the best possible measurements?
Click to expand...

So it is actually a AK4490 Dual Mono DAC and the actual LPF circuit is as per the attachment. I am just using the principles of the AK4497 schematic. The first resistor is 660 Ohms (double what is shown to compensate for the two DAC channels connected in parallel). It sounds very good but I wonder whether I am getting the best results with this configuration and whether I might get better results with a series connection?
Instinctively the series connection should provide better SNR?
 

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  • AK4490 LPF Wiring.JPG
    AK4490 LPF Wiring.JPG
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#13
I have a hot air station so removing and replacing the chip is not an issue but to be honest I have not even checked whether it's a drop in replacement.
Just trying to get the best possible out of the AK4490 at the moment.


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#15
I was thinking I should try the new 140dB Sabre next so not too bothered. Having said that there has been no sign of either the AK4497 or the Sabre 9038 thus far so I suspect it is a 6 month wait as a minimum before boards appear for these?


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#17
themystical said:
So this is the Cirrus way, see page 25 of the WM8740 Datasheet. Completely different but I suspect better.
https://www.cirrus.com/cn/pubs/proDatasheet/WM8740_v4.4.pdf


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Click to expand...



Ok so having studied this, it's no different in principle from the AKM method. This is still just running the two channels in parallel so I can't see where the 3dB improvement is coming from!?
Anybody know of any reference for a series connection which would end up doubling the voltage, not current?


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#20
n_dori said:
Fixed shcematic
Click to expand...



So I have been thinking exactly along these lines? The first stage is a differential circuit with an LPF filter. The second stage is a balanced to single ended converter which is unnecessary in my case because I need a balanced output. So I think in this schematic, either the left or the right channel (but not both) needs its analogue outputs inverted and whichever channel is inverted becomes the negative pin?
Is there somebody who can verify this?
If this works, it is very minimal modification to the DiyinHK board to get the mono output from the current L and R single ended outputs.
Appreciate your input n_dori


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